In the prior art a two-pass acoustic modulator has been used in the cavity of a folded-cavity laser for dumping the cavity to produce an output pulse of light. The output pulse from such a two-pass acoustic modulator is known to be intensity-modulated at twice the acoustic frequency of the acoustic modulator. The intensity modulation is the result of alternate destructive and constructive addition of two components of light that constitute the output signal, the frequency of one component being slightly higher than the frequency of light in the laser and the frequency of the other component being slightly lower.
Also known in the prior art are mode-locked lasers in which a short optical pulse that includes many cycles of the light frequency travels in the laser cavity, the pulse circulating back and forth in the cavity repeatedly. Pulses from mode-locked lasers have been used in the past for optical sampling in the observation of fast phenomena.